Common forms of refractive surgery include radial keratotomy in which a series of micro-incisions are made radially on the anterior surface of the cornea in order to modify its curvature, photo-reactive keratoplasty in which the surface of the cornea is flattened or steepened using an ablating laser beam, keratomileusis in which a lamellar portion of the cornea is removed and discarded or removed then reinstalled after reshaping its recipient bed and/or reshaping the portion itself by further lamellar resection. Each one of the above-mentioned procedures comprises a multi-step operation and suffers from a limited degree of precision.
In keratomileusis the lamellar cap is usually removed by means of a special scalpel such as the one available from Steinway Instrument Company Inc. of San Diego, Calif. under the brand name MICROKERATOME. This instrument comprises a stabilizing ring 100 which is held by vacuum against the cornea 101 and around the area to be resected, a plate 102 situated atop the ring which contacts the portion of cornea poking through the ring thereby flattening it 103 and securing its position at a specified height within the ring, and a blade 104 that can be translated linearly across the aperture of the ring. Accordingly, the cuts made by this instrument are not by themselves corrective since the section is of uniform thickness as shown in FIG. 1B. Either the sectioned bed or the sectioned cap must still be reshaped. In the case of myopia, a second smaller diameter section is taken from the bed, then the first section replaced. In the case of hyperopia, the first section is discarded, allowing the healing cornea to form a steepened surface. It would be advantageous to be able to modify the surface of the cornea in a single sectioning step, thereby reducing the time needed to perform the sergery and the time required to heal.